1. Field of the Invention
The invention relates generally to temperature control devices and, more particularly, but not by way of limitation, it relates to an improved form of tracking temperature controller for maintaining a first medium at the same temperature as that of another source.
2. Description of the Prior Art
The prior art includes various forms of temperature controller apparatus for utilization to control temperature around a predetermined set point in various types of heating, reaction chambers or vessels and diverse other exothermic processes. U.S. Pat. No. 4,288,854 is of general interest in that it teaches a temperature controller that senses a body temperature and then heats or cools the body in either of a high or low power mode, depending on previous heating and cooling cycle time. Thus, heating power is increased in response to the need for greater heat input to the controlled body. This teaching utilizes specific digital logic and control circuitry functioning in response to detected duty cycle periodicity to generate the required heating and cooling correction inputs to the controlled body. Still other patents of a general nature use programmed digital logic to control any of various parameters, e.g. U.S. Pat. No. 4,209,837, and these teachings function in old and well-known manner, utilizing various combinations of circuit components, to generate an error voltage proportional to a difference between a desired value of a physical parameter and its actual value, thereafter to provide correctional control output. Such prior art circuitry functions along the lines of basic servo control circuitry albeit that they function utilizing more sophisticated digital equipmentation.
Other patents of interest relative to the present invention are as follows: U.S. Pat. No. 4,234,410; U.S. Pat. No. 4,249,907; U.S. Pat. No. 2,310,955; U.S. Pat. No. 3,258,970; and, U.S. Pat. No. 3,761,690.